package com.baomidou.jobs.starter.router.strategy;

import com.baomidou.jobs.starter.model.param.TriggerParam;
import com.baomidou.jobs.starter.api.JobsResponse;
import com.baomidou.jobs.starter.router.IExecutorRouter;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 单个JOB对应的每个执行器，使用频率最低的优先被选举
 * a(*)、LFU(Least Frequently Used)：最不经常使用，频率/次数
 * b、LRU(Least Recently Used)：最近最久未使用，时间
 * <p>
 * Created by xuxueli on 17/3/10.
 */
public class ExecutorRouteLFU implements IExecutorRouter {

    private static ConcurrentHashMap<Long, HashMap<String, Integer>> jobLfuMap = new ConcurrentHashMap<Long, HashMap<String, Integer>>();
    private static long CACHE_VALID_TIME = 0;

    public String route(Long jobId, List<String> addressList) {

        // cache clear
        if (System.currentTimeMillis() > CACHE_VALID_TIME) {
            jobLfuMap.clear();
            CACHE_VALID_TIME = System.currentTimeMillis() + 1000 * 60 * 60 * 24;
        }

        // lfu item init
        // Key排序可以用TreeMap+构造入参Compare；Value排序暂时只能通过ArrayList；
        HashMap<String, Integer> lfuItemMap = jobLfuMap.get(jobId);
        if (lfuItemMap == null) {
            lfuItemMap = new HashMap<>(2);
            // 避免重复覆盖
            jobLfuMap.putIfAbsent(jobId, lfuItemMap);
        }

        // put new
        for (String address : addressList) {
            if (!lfuItemMap.containsKey(address) || lfuItemMap.get(address) > 1000000) {
                // 初始化时主动Random一次，缓解首次压力
                lfuItemMap.put(address, new Random().nextInt(addressList.size()));
            }
        }
        // remove old
        List<String> delKeys = new ArrayList<>();
        for (String existKey : lfuItemMap.keySet()) {
            if (!addressList.contains(existKey)) {
                delKeys.add(existKey);
            }
        }
        if (delKeys.size() > 0) {
            for (String delKey : delKeys) {
                lfuItemMap.remove(delKey);
            }
        }

        // load least userd count address
        List<Map.Entry<String, Integer>> lfuItemList = new ArrayList<Map.Entry<String, Integer>>(lfuItemMap.entrySet());
        Collections.sort(lfuItemList, new Comparator<Map.Entry<String, Integer>>() {
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2) {
                return o1.getValue().compareTo(o2.getValue());
            }
        });

        Map.Entry<String, Integer> addressItem = lfuItemList.get(0);
        addressItem.setValue(addressItem.getValue() + 1);
        return addressItem.getKey();
    }

    @Override
    public JobsResponse<String> route(TriggerParam triggerParam, List<String> addressList) {
        return JobsResponse.ok(route(triggerParam.getJobId(), addressList));
    }

}
